Efficiency is almost never (correctly) used anymore. It's useage in general has become less common since approximately the late 1960's. I know useage determines definition, but this is something serious students of the loudspeaker art & science would defend steadfastly, & the differences are worth noting. Sound & Vision Buyer's Guide 2001 (Glossary page 338) defines "efficiency" as "The percentage of electrical input power going to a speaker that is converted into acoustic energy; often used synonomously with the related concept of sensitivity." Not "is a synonym", and not "always interchangeable with", but rather "used synonmously". A girlfriend who has performed "wifely" functions can not successfully sue for divorce. Also it does not say "identical concept" or "same concept", but rather "related concept". The measurement units "percent" & "dB/watt/meter" are not always interchangeable, & not in this case. In this case "percent" expresses how much of an amplifier's power is converted into acoustic energy, while "dB/watt/meter" expresses a specific unit of sound pressure measured at a particular distance from the source with a specific measure of power applied. For instance 87% can not be compared to 87dB/watt/meter for (I hope) obvious reasons. In the former, 13% of the applied power is not converted into acoustic energy, whereas in the later, that percentage is unknown & undecipherable (form the information given, anyway). I respectfully request poster Gm to list the specific Vandersteen literature mentioned. Richard V. or anyone in his tech. dept. would agree with me & Sound & Vision. Likely the copy, if published by Richard's company, was written by an ad person who does not even know what absolute polarity is. Other reliable sources would be Brian Cheney, the San Francisco Bay Area Chapter secretary of the Audio Engineering Society (vmpsaudio@aol.com) or Galen Carol at Galen Carol Audio, who was in the technical dept. at JBL when it was known as James B. Lansing Co. If this all seems too trivial, I apologize, but as the great Jack Webb used to say, "Just the facts, m'am. Just the facts". This is a good thing about which hobbyists should know & agree upon the differences. Cheers.
